A mixer includes input channels for a plurality of microphone/line inputs as input signal series, and transmits an audio signal from each of the input channels to a mixing bus. The resultant audio signal from the mixing bus is outputted through a plurality of output channels being output signal series. In each input channel, frequency characteristics and a volume level are set, and further a send level for the transmission to the mixing bus is set.
In a conventional mixer, a function in which a plurality of channel faders each provided at respective input channels are put together as a DCA group, and the channel faders in the same group are operated together according to operation on a DCA fader is known. In this case, an output level actually used in volume adjustment in the input channel is a level in which a DCA level set by the DCA fader is reflected on a fader level set by the channel fader. In the conventional mixer, a position of a knob of the channel fader indicates the fader level. Further, it is known that the actually used output level is displayed by the position of the knob by moving, in response to an operation of a switch, the position of the knob of the channel fader to a position in which the DCA level of the DCA fader is reflected on the fader level (refer to PTL1). It becomes thereby possible to easily check the actually used output level by operating the switch. The DCA level set by the DCA fader is not reflected to the position of the knob of the channel fader as long as the switch is not operated, and therefore, it is possible to finely set the fader level by moving the knob of the channel fader.